This invention relates to a pneumatic tire, and more particularly to a pneumatic tire for, especially, a passenger car, which tire is capable of improving the steering stability thereof while maintaining the durability of belt layers at a level equal to that of the durability of a belt layer in a conventional pneumatic tire, without causing an increase in the weight of the tire.
Conventional pneumatic tires for a passenger car include, for example, a tire shown in FIG. 3. In this pneumatic tire, belt edge cushion rubber layers 14 are disposed between both end portions of an innermost belt layer 12a out of a plurality of belt layers 12 buried in a tread portion 11 and a carcass layer 13. Second fillers 19 are provided the parts of side wall portions 18 which are on the outer sides of both end portions 13a of the carcass layer 13 which extend into the radially outer portions of the tire. The end portions 13a are folded from the inner side of the tire to the outer side thereof around bead cores 16 buried in left and right bead portions 15, in such a manner that the folded parts of the carcass sandwich bead fillers 17 joined to outer circumferences of the bead cores 16. The second fillers 19 are provided so that inner circumferential portions of the second fillers 19 overlap the bead fillers 17 in the widthwise direction of the tire.
The belt edge cushion rubber layers 14 are provided to lessen the stress in the edges of the belt layers and improve the durability of the belt edge portions. The second fillers 19 are provided to heighten the rigidity (especially, the rigidity thereof in the circumferential direction of the tire) of the side wall portions 18 and improve steering stability. The belt edge cushion rubber layers 14 and second fillers 19 are generally formed of different kinds of rubber due to their different purposes.
Since it has become necessary in recent years that a vehicle has a higher performance and secures a sufficiently high safety, a pneumatic tire of the above-described construction must have a higher steering stability. Moreover, in order to follow the tendency in recent years for a vehicle to have decreased weight, it has been strongly demanded that the steering stability of a tire be improved with the durability of a belt layers being maintained at a level equal to that of the durability thereof in a conventional tire, without causing an increase of the weight of the tire.